The present invention relates to a system for sensing and automatically controlling the orientation of a work tool pivotally attached to a boom of a work vehicle.
A variety of work machines can be equipped with tools for performing a work function. Examples of such machines include a wide variety of loaders, excavators, tele-handlers, and aerial lifts. A work vehicle such as backhoe loader may be equipped with a tool, such as a loader bucket or other structure, for excavating and material handling functions. A boom attaches to the frame of the vehicle about a horizontal boom pivot, and the tool attaches to the boom about a horizontal bucket pivot. A vehicle operator controls the orientation of the tool relative to the boom by a tool actuator. The operator also controls the rotational position of the boom relative to the vehicle frame by a boom actuator. Both actuators are typically comprised of one or more double acting hydraulic cylinders and a corresponding hydraulic circuit.
During a work operation, such as lifting or transporting material with the tool, it is desirable to maintain an initial tool orientation relative to gravity to prevent premature dumping of material. To maintain the initial tool orientation relative to gravity, the operator is required to continually adjust the tool orientation as the boom is rotationally moved relative to the frame during a lifting operation, and as the vehicle frame changes pitch when moving over uneven terrain during a transport operation. The continual adjustment of the tool orientation requires a degree of operator attention and manual effort that diminishes overall work efficiency and increases operator fatigue.
A number of mechanism and systems have been used to automatically control the orientation of a tool such as a loader bucket. Various examples of electronic sensing and control systems are disclosed in U.S. Pat. Nos. 4,923,326, 4,844,685, 5,356,260, and 6,233,511. Control systems typical of the prior art utilize position sensors attached at various locations on the work vehicle to sense and control tool orientation relative to the vehicle frame. Unlike the typical prior art, the present invention makes use of an angular velocity sensor attached to the tool to sense and maintain a fixed work tool orientation relative to an initial orientation, independent of vehicle frame orientation. The result is a simpler control system and improved tool orientation control relative to gravity.
A number of angular velocity sensors suitable for use in the present invention are commercially available. Examples of these types of angular velocity sensor are disclosed in U.S. Pat. Nos. 4,628,734, 5,850,035, 6,003,373. One example of such an angular velocity sensors is the BEI GYROCHIP(copyright) Model AQRS, marketed by the Systron Donner Internal Division of BEI Technologies of California.
The object of the present invention is to provide for an improved system for sensing and automatically controlling the orientation of a work tool pivotally attached to a boom of a work vehicle.
The system automatically controls work tool orientation by making use of an angular velocity sensor attached to the tool to sense angular velocity of the tool relative to a global earth reference. A controller maintains the tool at a selected angular velocity.
The present invention comprises a work vehicle, a boom attached to the work vehicle, a tool pivotally attached to the boom, an actuator for controllably moving the tool about its pivot, the aforementioned angular velocity sensor, and a controller for processing data from the angular velocity sensor, and for commanding movement of the tool actuator. The illustrated embodiment also includes command input devices that an operator can manipulate to affect movement of tool actuator, and to activate a tool auto-hold function to maintain the tool in an initial orientation.
When the tool auto-hold function is enabled, the controller maintains the tool orientation by commanding the tool actuator to move the tool such that the angular velocity sensed is zero. In applications requiring greater tool orientation precision, the controller may be adapted to solve the integral for the angular velocity as a function of time to determine positional deviation from the initial orientation, and to command the tool actuator to move the work tool such that the orientation deviation is nearly zero. The controller is adapted to discontinue the tool auto-hold function when the operator manipulates the command input device corresponding to tool actuator movement. The controller resumes tool auto-hold function once the operator discontinues manipulation of the tool actuator controller, reestablishing the initial tool orientation at the new orientation affected by manipulation of the tool actuator controller. Additionally, the operator may manipulate an auto-hold command input device to selectively enable and disable the tool auto-hold function.